Acoustic wave elements such as film bulk acoustic resonators (FBARs) or surface acoustic wave (SAW) resonators have been used for bandpass filters in various circuits that process radio signals in the frequency band ranging from 45 MHz to 4 GHz typified by mobile phones.
As a method of mounting a functional element such as the acoustic wave element, there have been known a method that flip-chip mounts a chip including the functional element formed on the lower surface of the chip on a substrate as disclosed in, for example, Japanese Patent Application Publication Nos. 2015-204531, 2005-223580, 2015-103888, and 2016-58964. The functional element such as an acoustic wave element faces the upper surface of the substrate across an air gap. It has been known to provide an insulating film on the upper surface of the substrate to inhibit the short circuit between an inductor located on the upper surface of the substrate and the acoustic wave element as disclosed in, for example, Japanese Patent Application Publication No. 2016-58964.
The electronic components including, for example, the acoustic wave elements are desired to be smaller as the functions of mobile phones and smart phones increase. On the other hand, as the power of power amplifiers for transmitting radio waves becomes higher, higher power durability is desired. To achieve the electronic component having smaller size and higher power durability, it may be considered to enhance the heat release performance from the functional element. However, when the functional element faces the upper surface of the substrate across an air gap, heat fails to be released from the lower surface of the functional element.